Web turning device



March 3 1964 c. ALLANDER ETAL 3,127,080 h WEB TURNING DEVICE Filed Feb. 15, .1962

2g. 9 g 0 6 6 Je- 9/La 9 (K9 'L. e a a g e e g 6 %9 6 6 9 sea W9 erg.

INVENTORS: CLAES ALLANDER BY JAN-MATS ENEROTH ATTYS.

United States Patent M 3,127,080 WEB TURNING DEVICE Claes Allander, Bromma, and Jan-Mats Eneroth, Jonkoping, Sweden, assignors to Aktiebolaget Svenslta Flaktfabriken, Stockholm, Sweden Fiied Feb. 15, 1962, Ser. No. 173,582 Claims priority, application Sweden Feb. 18, 1961 1 Claim. (Cl. 226-97) The present invention relates to a web-turning device functioning like turning roll for web-shaped material and comprising an air distribution duct connected to an air supply means and port means of a special form for supplying air from said duct beneath the turning portion of said web.

For drying and other treatment of paper, cellulose and like web-shaped material, it has become more and more a common practice to advance the material web without employing mechanical conveyors and to let the Web be supported and advanced through the plant by means of the treatment medium which is directed against the web in the form of jets. In order to obtain the necessary evaporation surface within the space available, the material web is in most cases carried through the plant in a plurality of zigzag turns. For supporting the web at the turning points, the plants are equipped with the necessary number of rotatable turning rolls. In view of the fact that during the drying process the material web usually is subjected to considerable shrinking, it has proved difficult to adjust the rotary speeds of the different turning rolls such that they correspond accurately to the actual web speed at the roll in question. In spite of the arrangement of complicated and expensive differential gears and sliding clutch means, there is still always the risk that at some turning points the material web will slide on the turning roll causing surface roughening and quality deterioration.

It is a main object of this invention to overcome the aforesaid drawback by replacing the rotary turning rolls with a stationary air distribution duct. The invention is characterized in that the duct has a substantially semicircular cross-section and that the arched portion of the mantle surface facing the turning web is perforated, and further in that the duct on each side of said perforated portion of the mantle is provided with a longitudinal slot with such a shape that the air blown out forms an air curtain directed towards the web to thereby partition a space between the web and the duct in order to maintain in said space a static overpressure sufficient for turning the web around the ducts without friction.

A preferable embodiment of the invention is characterized in that said two slots are shaped to impart to the air curtains directed towards the web an oblique, towardsthe partitioned-space pointed flow direction.

The invention will now be described more in detail with reference to the accompanying drawing showing a drying plant for paper equipped with turning means according to the invention, and wherein FIG. 1 shows a vertical longitudinal section of the drying plant,

FIG. 2 shows a front view of a turning means, and

FIG. 3 shows a cross-section of the turning means along the line 3--3 in FIG. 2.

In the drawing 1 designates a drying plant for a paper web 2 advanced through the plant in a plurality of horizontal turns 2a, 2b, 2c, and 2d, etc. The necessary 3,127,080 Patented Mar. 31, 1964 amount of treatment medium is supplied by a plurality of blowing boxes 3 disposed between the web turnings, the said treatment medium being blown out against the web in the form of fine jets through the perforated walls of the boxes facing the web, said jets in the embodiment shown both supporting the web and advancing the same. The medium blown against the web is discharged through ducts 4 disposed between said blowing boxes and conducted to circulating and heating means (not shown) connected to said blowing boxes and discharge ducts. Turning means 5 are mounted in each turning point of the web and comprise according to the invention an air distribution duct of a construction shown in detail in FIGS. 2 and 3. Said ducts, which are supplied with air at the necessary pressure from a means (not shown) through pipes 6 connected to both ends of the ducts, have a straight wall 7 and a semicircularly curved wall 8 facing the material web. The last mentioned wall 8 is provided with a plurality of outlet openings 9 uniformly distributed over the entire length of the duct. The duct has furthermore on each side of said perforated mantle surface adjacent to the straight wall 7 a longitudinal slot 10 with such shape that the air blown out forms an air curtain directed towards the web to thereby partition a space between the web and the duct in order to maintain within said space a static overpressure sufficient for turning the web around said duct without friction. Said slots 10 are-as in the embodiment shown-preferably given such shape as to impart to said air curtains an oblique, towards-the-partitioned-space pointed flow, direction. The invention has above been described in connection with a drying plant wherein the material web is conveyed in an airborne manner, which is the most essential field of application for this invention. The invention may, of course, even be applied in drying plants employing conveyors for advancing the web.

What we claim is:

A web turning device, comprising in combination, a stationary substantially semi-cylindrical shell around which said web turns, the interior of said shell being supplied with air under pressure, the arcuate surface of said shell over which said web passes being provided with a plurality of small apertures opening through the shell beneath the web thereon, and said shell at the ends of the surface over which the web passes being provided with transverse slotted apertures extending across substantially the full width of the web, the pressure of air within said shell being sufficient to maintain an air layer between said web and shell which completely separates the web from the shell for substantially frictionless passage of the web over the arcuate web-supporting portion of the shell, said two end slots having an angular inclination toward the arcuate portion of said web which is supported above the arcuate supporting portion of said shell to assist in maintaining the supporting layer of air beneath said web by directing transverse air curtains from the end slots mutually toward each other in said arcuate supporting layer of air between the web and the shell.

References Cited in the file of this patent UNITED STATES PATENTS 1,630,713 Meyer May 31, 1927 2,736,106 Offen Feb. 28, 1956 2,908,495 Andrews et a1 Oct. 13, 1959 

